236 NOTES ON THE PERMIAN SYSTEM OF 



friable, thin-bedded limestone, with occasional beds of fine- 

 grained and of oolitic structure. 



Probable thickness 100 feet. 



Characteristic Fossils. — Mijalina Hausmcumi, Goldf. ; 3/yo- 

 conclia costata, Brown ; Axinus dubius, Schloth. ; Littorina helicina^ 

 Schloth. 



Loc. Roker, Sunderland Docks, Hartlepool. 



2. BoTRYOiDAL-LiMESTONE. — Tliis divisiou consists of beds, 

 chiefly of a coralloid, spheroidal, botryoidal, finely-laminated, 

 close-grained, and highly crystalline structure, interstratified with 

 close-bedded, compact layers, and others wdiich are earthy, 

 friable, and pulverulent. 



Thickness probably more than 150 feet. 



Char. Foss. — Myalma Ilausmanni, Goldf.; Myoconcha costata; 

 Axinus diihius, Schloth. ; Leda speluncaria, Geinitz ; Littorina 

 heliciiia, Schloth. Numerous Entomostraca and Foraminifera. 



Loc. Coast of Durham from Marsden Bay to Roker; patches 

 occur between Hendon and Ryhope, and North and South of 

 Black Halls; Cleadon Hills, Fulwell Hill, Building Hill, &c.. 



Middle. 



3. Cellular and Shell-Limestone. — An amorphous irre- 

 gular deposit of highly crystalline or saccharine limestone, 

 occasionally full of small, irregular cavities, partially or entirely 

 filled with a fine earthy yellowish powdery substance ; other 

 parts present the appearance of being formed of shapeless frag- 

 ments of compact limestone imbedded in a completely investing 

 matrix, without taking the form of a true breccia. Occasion- 

 ally, however, large angular masses of finely laminated limestone 

 are imbedded in it, especially towards its highest portion, where 

 it also gradually becomes more earthy, and in some localities 

 regularly bedded, and oolitic. The uj^per beds are oftentimes 

 strongly undulated and much broken up, and the fissures filled 

 with masses of breccia derived from superincumbent strata. 



Its thickness is probably more than 150 feet. 

 A few specimens of Axinus dubius, Schloth. ; and traces of Pcd- 

 o'onisci, 6cc., have been found in some of the upper regular beds. 



